Is it true that toilets and sinks in the southern hemisphere drain counter-clockwise, or is that an urban myth?

Very true, demonstrations on the equator prove the fact with a bucket of water draining through a hole in the bottom either side of the exact location for a fee.

Iz true.

I noticed last time was sick in Buenos Aires 

Maybe Gravity

From what I learned in school, it is not true. I double-checked on Scientific American and Snopes to verify that it is a myth. I'll let Element explain why.

Thanks, Jane. The Coriolis effect is only relevant for large scale events, typhoons, hurricanes etc. Toilets flushing are determined by the direction that the water outlets are aimed. For an explanation of the Coriolis effect...film at 11:00.

I have been at the Equator and the water does drain counter clockwise.  I'm not sure about toilets since they mostly just go straight down, even above the Equator.  

If you very carefully isolate a small body of water from ALL outside influences, the minuscule Coriolis effect can be detected. In a bathroom fixture, it's almost impossible to achieve.

It is an old myth.

I have seen the vortex sometimes stop then start again in the opposite direction, and I have also artificially reversed it by swirling the water by hand. The rotation is probably determined by the shape and size of the sink and outlet, and perhaps also the depth of water.